Fix issue with only a single feature flag defined.

- Ensure that the last item doesn't have a trailing comma.
- Update .gitignore to ignore test values for now

.gitignore

@@ -3,3 +3,4 @@
 .cr-index
 # Create a folder for placing user test files (Useful for the Dev Container)
 values/*
+test_values.yaml

charts/self-host/templates/pre-install-hook-feature-flags.yaml

@@ -7,8 +7,11 @@ data:
   flags.json: |
     {
       "flagValues": {
+        {{- $first := true }}
         {{- range $key, $value := .Values.featureFlags }}
-        "{{ $key }}": {{ $value | quote }},
+          {{- if not $first }},{{ end }}
+          "{{ $key }}": {{ $value | quote }}
+          {{- $first = false }}
         {{- end }}
       }
     }